Scoring Personalized Needs in Clostridium Difficile Infections for Fidaxomixin Therapy

Medical world is nowadays witnessing a sudden increase of the incidence of infections by Clostridium difficile (DCI). This is due in part to the prolongation of survival of patients with major comorbidities like solid tumor malignancies and lymphomas but also to the widespread intake of proton pump inhibitors and of wide-spectrum antimicrobials. It is highly probable that isolates of C.define causing this pandemic are genetically different than isolates of the same species predominating 20 years ago. This hypothesis is developed based on data of the epidemiology of CDI: in old times administration of clindamycin and ampicillin were the main drivers of CDI; recent studies report fluoroquinolones, 2nd and 3rd generation cephalosporins and even vancomycin (i.e. a drug of choice for CDI) to be linked with the development of CDI.

One major hurdle in management of CDI is relapse; the risk of relapse is reported as 15-20% after the first episode; however it is geometrically increased to even 60-80% after the second episode. As a consequence, management of CDI becomes a major health problem.

Fidaxomicin is a novel compound active against species of C.dificille. Results of two recent double-blind, randomized, large scale clinical studies have shown that oral treatment for 10 days with fidaxomicin 200mg bid was non-inferior to oral treatment with vancomycin 125mg q6h. However, the risk of relapse after treatment with vancomycin was close to 25% and with fidaxomicin close to 15%. This difference was statistically significant in both trials outscoring the superiority of fidaxomicin over vancomycin for the management of CDI. Moreover, meta-analysis has shown a significant reduction in mortality by fidaxomicin.

Despite proven superiority, prescription of fidaxomicin is limited to few cases mostly due to high cost. In many countries prescription is restricted to cases of relapsing CDI. Clinical feeling coming both from post-marketing experience as well as from published evidence supports the use of fidaxomicin for cases with risk of death and overt risk of relapse. However, molecular analysis of the C.difficile pathogen cannot be used as a tool for the prediction of relapse since in relapse cases pathogens carry less than 2 single nucleotide variants of the initial isolate. SPECIFY is aiming to develop a score using both clinical and genetic and biomarker data that can efficiently discriminate patients at risk of severe CDI and at risk of relapse of CDI. This score can become in future a tool to discriminate patients at need for treatment with fidaxomicin instead of traditional treatment with metronidazole/vancomycin.